Bacteriophage-based diagnostics and therapeutics have been recognized as tools to combat bacterial infections for nearly a century. Wip1 (for worm intestinal phage 1) is a recently identified phage that infects the pathogen Bacillus anthracis and was isolated from the intestinal tract of Eisenia fetida worms [Schuch, R., et al., Prevalence of Bacillus anthracis-like organisms and bacteriophages in the intestinal tract of the earthworm Eisenia fetida. Applied and environmental microbiology, 2010. 76(7): p. 2286-94]. It is a tailless, double-stranded DNA phage possessing an internal lipid membrane beneath an icosahedral protein coat [Schuch, R. F. V. A., The Secret Life of the Anthrax Agent Bacillus Anthracis: Bacteriophage-Mediated Ecological Adaptations. PLos One, 2009. 4(8): p. e6532]. These features indicate that Wip1 belongs to the family Tectiviridae, a relatively rare phage group with surprising structural similarity to and a proposed evolutionary lineage with the mammalian adenovirus [Merckel, M. C. H., J. T.; Bamford, D. H.; Goldman, A.; Tuma, R., The Structure of the Bacteriophage PRD1 Spike Sheds Light on the Evolution of Viral Capsid Architecture. Molecular Cell, 2005. 18: p. 161-170, Bamford, D., Evolution of Viral Structure. Theoretical Population Biology, 2002. 61(4): p. 461-470.]. The Tectiviridae family consists of six isolates that infect gram-negative bacteria, including PRD1 [Olsen, R. H. S., J.; Gray, R. H., Characteristics of PRD1, a Plasmid-Dependent Broad Host Range DNA Bacteriophage. Journal of Virology, 1974. 14(3): p. 689-699], and six that infect gram-positive bacteria, including Bam35, Gil16, AP50, and Wip1 [Schuch, R., et al., Prevalence of Bacillus anthracis-like organisms and bacteriophages in the intestinal tract of the earthworm Eisenia fetida. Applied and environmental microbiology, 2010. 76(7): p. 2286-94; Ackermann, H. W. R., R.; Martin, M.; Murthy, M. R.; Smirnoff, W. A., Partial Characterization of a Cubic Bacillus Phage. Canadian Journal of Microbiology, 1978. 24: p. 986-993; Verheust, C., N. Fornelos, and J. Mahillon, GIL16, a new gram positive tectiviral phage related to the Bacillus thuringiensis GIL01 and the Bacillus cereus pBClin15 elements. Journal of bacteriology, 2005. 187(6): p. 1966-73; Nagy, E. P., B.; Ivanovics, G., Characteristics of Phage AP50, an RNA Phage Containing Phospholipids. Journal of General Virology, 1976. 32: p. 129-132]. While PRD1 has been studied in detail, tectiviruses that infect gram-positive bacteria are not as well characterized.
Wip1 phage exhibits a very narrow host range and is highly specific to B. anthracis [Schuch, R., et al., Prevalence of Bacillus anthracis-like organisms and bacteriophages in the intestinal tract of the earthworm Eisenia fetida. Applied and environmental microbiology, 2010. 76(7): p. 2286-94], the notorious biothreat agent and gram-positive bacterium that causes anthrax disease. The current gold standard for identifying suspected B. anthracis involves testing for γ phage sensitivity [Abshire, T. G., J. E. Brown, and J. W. Ezzell, Production and validation of the use of gamma phage for identification of Bacillus anthracis. Journal of clinical microbiology, 2005. 43(9): p. 4780-8; Anthrax Q & A: diagnosis. 2002; Available from: www.bt.cdc.gov/agent/anthrax/faq/diagnosis.asp]. However, using γ as a diagnostic tool can lead to false positives due to the susceptibility of several Bacillus cereus strains to infection by this phage [Schuch, R. and V. A. Fischetti, Detailed genomic analysis of the Wbeta and gamma phages infecting Bacillus anthracis: implications for evolution of environmental fitness and antibiotic resistance. Journal of bacteriology, 2006. 188(8): p. 3037-51; Schuch, R. N., D.; Fischetti, V. A., A bacteriolytic agent that detects and kills Bacillus anthracis. Nature, 2002. 418: p. 884-889]. Recent studies have shown that the host range of γ is less specific to B. anthracis than those of tectiviruses Wip1 and AP50 [Schuch, R., et al., Prevalence of Bacillus anthracis-like organisms and bacteriophages in the intestinal tract of the earthworm Eisenia fetida. Applied and environmental microbiology, 2010. 76(7): p. 2286-94; Sozhamannan, S., et al., Molecular Characterization of a Variant of Bacillus anthracis-Specific Phage AP50 with Improved Bacteriolytic Activity. Applied and environmental microbiology, 2008. 74(21): p. 6792-6796]. For example, Bacillus cereus ATCC 4342 is sensitive to infection by γ phage but not to infection by either Wip1 or AP50. Additionally, the γ diagnostic phage yields plaques on B. anthracis ΔSterne only after 5 days, whereas Wip1 plaques can be detected after just 12 hours post infection [Schuch, R., et al., Prevalence of Bacillus anthracis-like organisms and bacteriophages in the intestinal tract of the earthworm Eisenia fetida. Applied and environmental microbiology, 2010. 76(7): p. 2286-94].
Wip1's high specificity to B. anthracis is likely mediated by the initial recognition and binding of the virus to the host cell. Receptor binding proteins on the phage coat interact very specifically with receptors exposed on the surface of the bacterium [Haywood, A. M., Virus receptors: binding, adhesion strengthening, and changes in viral structure. Journal of virology, 1994. 68(1): p. 1-5]. For tectiviruses, the receptor binding protein assembles with other phage proteins into a protruding complex that extends from each particle vertex [Sokolova, A., et al., Solution structure of bacteriophage PRD1 vertex complex. The Journal of biological chemistry, 2001. 276(49): p. 46187-95]. In the PRD1 spike complex, two elongated proteins, monomeric receptor binding protein P2 and trimeric spike protein P5, form two separate spikes that each protrude from penton base protein P31 [Bamford, J. K. B., D. H., A New Mutant Class, Made by Targeted Mutagenesis, of Phage PRD1 Reveals That Protein P5 Connects the Receptor Binding Protein to the Vertex. Journal of virology, 2000. 74(17): p. 7781-7786; Huiskonen, J. T., V. Manole, and S. J. Butcher, Tale of two spikes in bacteriophage PRD1. Proceedings of the National Academy of Sciences of the United States of America, 2007. 104(16): p. 6666-71; Mindich, L. B., D.; McGraw, T.; Mackenzie, G, Assembly of bacteriophage PRD1: particle formation with wild-type and mutant viruses. Journal of virology, 1982. 44(3): p. 1021-1030; Xu, L. B., S. D.; Butcher, S. J.; Bamford, D. H.; Burnett, R. M., The Receptor Binding Protein P2 of PRD1, a Virus Targeting Antibiotic-Resistant Bacteria, Has a Novel Fold Suggesting Multiple Functions. Structure, 2003. 11: p. 309-322].
Spike complex protein components have also been identified for Bam35, a tectivirus that infects gram-positive Bacillus thuringiensis [Gaidelyte, A., et al., The Entry Mechanism of Membrane-Containing Phage Bam35 Infecting Bacillus thuringiensis. Journal of bacteriology, 2006. 188(16): p. 5925-5934]. By threading Bam35 gene products onto PRD1 X-ray structures, it was determined that gp28 is homologous to spike protein P5 and that gp29 is homologous to the C-terminal half of receptor binding protein P2 [Laurinmaki, P. A. H., J. T.; Bamford, D. H.; Butcher, S. J., Membrane Proteins Modulate the Bilayer Curvature in the Bacterial Virus Bam35. Structure, 2005. 13: p. 1819-1828; Ravantti, J. J. G., A.; Bamford, D. H.; Bamford, J. K., Comparative analysis of bacterial viruses Bam35, infecting a gram positive host, and PRD1, infecting gram-negative hosts, demonstrates a viral lineage. Virology, 2003. 313: p. 401-414. In addition, gp28 and gp29 were determined to reside on the surface of Bam35 from phage aggregation and neutralization assays using polyclonal antibodies [Gaidelyte, A., et al., The Entry Mechanism of Membrane-Containing Phage Bam35 Infecting Bacillus thuringiensis. Journal of bacteriology, 2006. 188(16): p. 5925-5934]. However, competitive binding assays using both recombinant and dissociated surface proteins were inconclusive, and a Bam35 receptor binding protein could not be identified.
The described invention addresses these problems, and provides recombinant phage proteins, and uses thereof, to identify and treat pathogenic bacteria.